everywhere. and you may surprised to learn who's watching you. can they make us safer? >> high alert superstorm. tornados, record temperatures, we go inside one man's desperate race to save our planet. >> we will never give up. >> keep it right here, america. "nightline" is back in 60

>> good evening. and thanks for joining us. we heard the dramatic story for days now, how one man went to check on his cherished boat and got the surprise of his life when he encountered one of the alleged bombing suspects. now for the first time today, that man david henneberry recounts the shocking turn of events.

more on the latest developments. >> he is the man who owned the boat that played a starring role in this saga. >> the vessel iron clon named the slipaway 2 seen in this driveway in a backyard in water town with the suspect dzhokhar tsarnaev in a showdown with police. he gave an exclusive internet to the local boston affiliate. >> i look in the boat and i see blood. a good amount of the blood. henneberry stepped outside to check his beloved boat and that's when he saw it. my eyes wept to the other side of the engine box. there's a body. >> at that moment, what did you do?

what were you thinking at that moment? >> oh, my god. i know i took three steps up the ladder. i don't remember stepping down off the ladder. this hits you more afterwards. my god, he probably slept last night. i don't know. it's surreal. >> he ran inside, called 911 and then the cavalry arrived. tonight, four days later, the young man who had been upgraded from serious condition. he said he only joined the bombing plot a week beforehand. they were inspired, h ehas reportedly said by an anti-american cleric, both of them angry about american policy in iraq and afghanistan.

>> my son was muslim, that's it. >> today, their mother flat-out denied her children could be involved. >> what happened is a terrible thing, but i know that my kids had nothing to do with this. i know it. i am mother. i have -- i know my kids. >> reporter: but for those of us more inclined to believe the official version of things, the nagging questions all linger around younger brother dzhokhar. it is a mystery that only got deeper today as friends released video of him doing a robot dance. we have essentially become a nation of armchair shrinks asking how could this kid dancing like a goof be the same one on this surveillance tape walking calmly through crowds of innocent people allegedly with a bomb packed with shrapnel in his backpack. >> this is where the brothers lived here on the top floor of this building. >> for days, we've been scouring

dzhokhar's life, patrolling the neighborhood where he lived with his brother, interviewing people who knew him. . >> he was a quiet guy. never really spoke much. never really spoke politics. >> he was the nicest kid. every single time i saw him, he would make sure to say hi. >> we had acting claz togethss . he was always funny and contributed. it never seemed like there were any warning signs. >> and to a one, they say the same thing. he was a sweet kid, avid wrestler with a little bit of a taste for weed. >> i have nothing bad to say about him, nothing. just a regular teenager, full of life is, full of dreams. >> gilberto jr. who owns an auto body shop near their apartment, he said there was one time he saw his young friend change. that's when his older brother was around. >> he was very quiet. he didn't say a word next to his brother. just say hi.

then once he was leave, you know, see you later. >> the dominant theory is that dzhokhar's older brother steered him wrong. the boxing, the increasingly devout muslim. if true, that would make this case fit in with plenty of others, the d.v. sniper, the alleged craigslist killer where a charismatic use usually older man accused of bringing a younger more vulnerable one along a homicidal mission. could it be the teenage brain? it's not fully developed. >> if i'm not 19 years old, the place where i have my impulses and desires, that's developed. but the part of my brain that regulates that, not fully developed. >> you might make decisions based more on an impulse than hmm, let me think from that a

little bit? >> does that mean he shouldn't be held responsible? >> there's some moment of availability or immaturity. does that mean what they don't know what they're doing is wrong? i wouldn't say that. >> this is intrigue, of course, but it's not a full explanation. the hard truth is we may never know how this dzhokhar, the goofy kid turned into this dzhokhar, the alleged terrorist. which is why for many, the story of dave henneberry is so appealing. it gives us some comforting certainty. one man who simply did the right thing. >> people are calling you a national hero. >> incidental hero. i hate to use cliches, but the people they killed, if they can get some -- >> reporter: you know, in many way, they do.

>> then i'm at peace with it, you know? >> reporter: for "nightline," this is dan harris in boston. >> our thanks to dan harris for that. well, next up, they're. co-ing to the skies close to you. but will they make us safer. so, this board gives me rates for progressive direct and other car insurance companies? yes. but you're progressive, and they're them. yes. but they're here. yes. are you...? there? yes. no. are you them? i'm me. but those rates are for... them. so them are here. yes! you want to run through it again? no, i'm good. you got it? yes. rates for us and them -- now that's progressive. call or click today.

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as the city of boston shut down friday, one question kept

rearing its head. would law enforcement use a drone to help locate and capture the suspects? from controversial u.s. attacks on alleged terrorists in pakistan and afghan sfan to do it yourself gadgets you can buy on the internet, dproens seem to be everywhere. we went to find out who's watching you. pilots with the miami-dade's police department are assembling their newest tool in law enforcement. this is one of two drones in their arsenal and carries a payload of a single camera. >> it basically assists us in getting an aero view for the ground units, the incident commanders and first responders on the scene. so that they can better prepare to approach a situation. >> miami-dade is one of more

than a dozen law enforcement agencies which are incorporating drones into daily operations. although their use is heavily regulated. >> we can't just sit and say we're going to fly this thing from the station and we're going to surveil the city. that doesn't work that way. we can't fly over populated areas or near highrises. >> straps in place? >> check. >> reporter: "nightline" recently visited during an exercise as the mav flew in support of a s.w.a.t. team operating on the ground. in this simulation, a suspect has escaped from custody and the mav will be used to see in real time what is happening in the search. as the mav gets into position over the area where the suspect is believed to be, its cameras

capture himsprinting across a building and into a clearing. the images from the drone help the incident commander guide the s.w.a.t. team into position. >> there's a building on the left side of the roadway. the subject was seen run into the doorway along the western wall. >> reporter: with the drone overhead and the s.w.a.t. team outside the door, the suspect is quickly apprehended. >> he's surrendering right now. >> we're hoping to use this for tactical situation where is we have somebody shooting at police. we don't want to put any plifs in danger. >> reporter: there are growing concerns about privacy. >> what we don't want to see is drones used to hover over our neighborhoods 24/7, keeping track of everywhere that we drive or walk. and the technology is there to do that. >> reporter: the faa estimates that some 10,000 commercial drones will be flying in the nation's skies within five years. >> look to the future, look to

the skies. what do you see? >> i see hundreds of thousands of vehicles being manufactured every year. >> banking on that growth is retired air force colonel and f-4 pilot jerry lemieux. >> when you think about the future, focus on the hundreds of commercial applications that these vehicles can be used for, such as agriculture. the news media is big, sports events. >> lemieux has just started up the first unmanned vehicle university. most of the teaching is done online, honoring courses in radar sensors, project management and mission design. as well as intensive weekend programs. and for those like justin woody who want to learn how to fly unmanned aerial vehicles, the university offers a three-day hands-on course. >> in the future, what i want to do is get into what they call precision agriculture, so i could go and help spot the troubled areas in the fields.

and help the farmers increase their crops. >> our turn? >> reporter: "nightline" dropped in on the latest session held at a model airplane field in sarasota, florida. i had practiced on a computer simulator before arriving and my instructor has 40 years of experienced, launched the fantasticed wing drone called a sky hawk. i took over the controls. wearing goggles, i see what the sky hawk sees. >> turn around 180 degrees and we're going to heading west. >> there's the airport. >> i made a few laps over the airstrip and then justin brought the sky hawk in for a landing. >> just keep this level. perfect. >> wow, justin, perfect. >> but working with drones isn't all about flying. with the aerial cameras and other sensors, the university gives students a chance to

operate those systems as well, using a helicopter-like drone that can hover. >> this one stays up about 12 minutes all by itself. >> this drone carried a camera that could shoot videos and stills. >> photographs give much higher resolution than video. >> as more and more drones take to our skies, congress has ordered the faa to come up with rules to fully integrate drones into the nation's air space by 2015. and jerry lemieux and his unmanned university will be standing by, controller in hand with the next generation of remote pilots. >> our thanks to martha for that. next, record temperatures are being felt around the world. we'll meet one man who is not surprised. [ male announcer ] a car that can actually see like a human, using stereoscopic cameras.

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if anyone in the world of climate science has the right to say i told you so, it may well be one of the nation's leading environmentalists. he has been been writing about

global warming for almost 25 years. and now some of his predictions have come to pass. super charged storms and droughts and a disappearing arctic, all brought on by the highest temperatures in recorded history. so for earth day, he sat down with my co-anchor bill weir for a look at the state of our planet by the numberses. >> there are just three numbers, but taken together, they represent a startling new equation for life on this planet as we know it. the first number is 2. as in 2 degrees celsius. >> that's how much the word's agreements and governments agreed we could let the  away with it. >> at the last climate summit, that was literally the only thing everyone could agree on. the u.s., china, russia, europe, even the oil-rich arab emirates all signed up to the belief if the planet warms by more than 2 degrees, the human race is screwed. even the ceo of exxon finally

admits that pumping carbon into the air warms the planet. >> not disputing that it will have an impact. it will have a warming impact. >> how much can we burn and stay within those 2 degrees? scientists say it is around 565 gigatons. or 565 billion tons, which sounds like a lot. >> a billion tons of something is a lot. but at the rate we're burning carbon now, we blow past that in about 14 years. so that's a bad number. >> but the last number is new and even scarier. it's how much carbon fuel the world has in reserve. how much it could burn without looking for any more. a team of anl lalysts in britai pored over all the numbers and

we have 2,795 gigatons. that's five times what they think they can burn. but they're going to burn it. >> we will never give up. >> reporter: he organizes and agitates and lobbies for a tax on carbon. he gets arrested for protesting that big new pipeline from canada. and tries to convince colleges to dump their oil company stock. >> so to somebody who says it's a very common political phrase, we need an all of the above strategy, we need clean energy, solar panels, but we also need the keystone xl pipeline because our economy depends on it. and people in emerging markets need to eat. to that you need to say? >> we've got to change because our economy depends on changing. if we let global warming get out of hand, the effects on our economy are equivalent to world war 1, world war ii, and the great depression combined.

we look back an the first earth day in 1970. 20 million americans were in the streets, 1 in 10 of the current population then. that's the kind of movement we're going to need if we're going to stand up to the power of this industry and make the change that we need. >> our thanks to bill weir for that report. and thank you for watching abc news. tune into "good morning america" tomorrow. as always, we're online at abcnews.com. hey! did you know that honey nut cheerios

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